Search with the plugin give different results

Hello, I noticed a strange behaviour.
When I go on the search bar (that i filtered within certain post category) the results are correct, but if I hit enter or the magnifier icon i got different result. It seems that the magnifier icon is connected with the default search engine and not with the plugin one. Why is that?

For example you can go here if you search for the word “carciofo” you have 7 result in the ajax select, but if you hit enter or the search icon you go to a different page with 40 different results.

Please let me know.
Thank you